This invention relates to a new and improved noise attenuating panel and more particularly, to a honeycomb panel having a perforated facing sheet with perforations of a size equal to or smaller than the normal cell size allowing communication between the core enlarged cell area and the atmosphere adjacent to the noise to be attenuated.
In making sound suppressive honeycomb sandwich panels which are exposed to the sound of jet engines and other noise producing mechanisms, it is common practice to provide a honeycomb sandwich structure wherein a central imperforate backing layer of a thin sheet of suitable material is mounted to one face of the core having a multiplicity of cells of equal and uniform size and a facing sheet of thin perforated sound pervious sheet material is applied to the other core surface.
Panels of this type construction, although satisfactory for some frequencies, are found to be an inefficient noise attenuator over a broad range of frequencies customarily encountered in aircraft jet engines.